1. Field of the Invention
This invention relates to and has among its objects the provision of novel methods for improving the baking properties of unbleached cake and bread flour. Another object of the invention is to provide a process for the controlled swelling of starch. Further objects of the invention will be evident from the following description wherein parts and percentages are by weight unless otherwise specified.
2. Description of the Prior Art
As a matter of custom in the United States wheat flour is normally bleached with chlorine gas prior to its use in baking cakes. Bleaching the wheat flour improves the texture, grain, volume, and eating quality of cakes produced therefrom. Furthermore, the color of white cake is improved when bleached flour is incorporated into the cake mix. As a result of the use of bleached flour, Americans have grown accustomed to cakes possessing the above-mentioned properties. For this reason and the fact that the chlorination process is both practical and economical, the use of bleached flour is firmly embedded in the American cake-baking industry.
In recent years, however, chemical treatments and chemical additives have become suspect and it is desirable to avoid such treatments and additives wherever possible. In addition, many foreign countries prohibit the use of bleached flour in their cake products. As a result, these countries do not import American products such as cake mixes and the like which contain chlorinated flour.
Alternatives to bleaching the flour have been actively sought over the last few years. The alternative treatments must avoid the use of chlorine, and chemicals in general, but still produce flour which will yield the type of cakes customarily obtained with bleached flour. One alternative to the chlorination method is to subject the flour to specified temperatures for limited periods of time. All of the known methods require a preliminary treatment. For example, in U.S. Pat. No. 3,490,917 normal soft wheat flour or starch is subjected first to air classification to obtain flour containing a major proportion of free starch granules or granules substantially free from enveloping gluten. The treated material is heated at a temperature of 100.degree. to 140.degree. C. for about 30 minutes to a maximum period such that no dextrinisation of the starch occurs. Then, the treated flour or starch is combined with dried viable gluten to give a flour useful in cake and sponge recipes. Recently, in British Pat. No. 1,499,986 it was shown that the preliminary air-classification step is unnecessary.
The methods of U.S. Pat. Nos. 1,452,871 and 3,974,298 (hereinafter referred to as '871 and '298, respectively) begin with a dehydration step. Thus, in '871 flour is dried under vacuum at 45.degree. C. to the exclusion of atmospheric air and under constant agitation and then rapidly and strongly cooled to zero degrees (centrigrade) or less under vacuum with constant agitation and in the absence of atmospheric air.
In the process of '298 whole wheat, or a milling intermediate, is dried to a moisture content of 6% or less and heated at 100.degree. to 140.degree. C., or 100.degree. to 200.degree. C. in the case of a milling intermediate, for a sufficient period. The treated whole wheat is cooled and then ground to produce flour. It is noted in the specification that departure from the teachings will yield a flour which is not a suitable replacement for chlorinated flour.
Hard wheat flour has been subjected to various heat treatments to improve bread-making or cake-making properties. According to U.S. Pat. No. 3,428,461 bread flour (i.e., hard wheat flour) can be heated at 66.degree. to 182.degree. C. for about 1 minute to 17 hours, preferably at 121.degree. to 182.degree. C. for about 10 to 80 minutes to render it suitable for cake mixes. Heating whole wheat at about 50.degree. to 80.degree. C. gives mild improvement in the bread-making properties of the resulting flour ('298).